Poly(p-phenylenevinylene)s derivatives containing a new electron-withdrawing CF₃F₄phenyl group for LEDs

New PPV derivatives which contain electron-withdrawing CF₃F ₄phenyl group, poly[2-(2-ethylhexyloxy)-5-(2,3,5,6-tetrafluoro-4- trifluoromethylphenyl)-1,4-phenylenevinylene] (CF₃F ₄P-PPV), and poly[2-(4-(2-etylhexyloxy)-phenyl)-5-(2,3,5,6- tetrafluoro-4-trifluoromethylphenyl)-1,4-phenylenevinylene] (P-CF ₃F₄P-PPV), have been synthesized by GILCH polymerization. As the result of the introduction of the electron-withdrawing CF ₃F₄phenyl group to the phenyl backbone, the LUMO and HOMO energy levels of CF₃F₄P-PPV (3.14, 5.50 eV) and P-CF ₃F₄P-PPV (3.07, 5.60 eV) were reduced. The PL emission spectra in solid thin film are more red-shifted over 50 nm and increased fwhm (full width at half maximum) than solution conditions by raising aggregation among polymer backbone due to electron withdrawing effect of 2,3,5,6-tetrafluoro-4-trifluoromethylphenyl group. The EL emission maxima of CF₃F₄P-PPV and P-CF₃F₄P-PPV appear at around 530-543 nm. The current density-voltage-luminescence (J-V-L) characteristics of ITO/PEDOT/polymer/Al devices of CF₃F ₄P-PPV and P-CF₃F₄P-PPV show that turn-on voltages are around 12.5 and 7.0 V, and the maximum brightness are about 82 and 598 cd/m², respectively. The maximum EL efficiency of P-CF ₃F₄P-PPV (0.51 cd/A) was higher than that of CF ₃F₄P-PPV (0.025 cd/A).